China has reported some cases of the more infectious Omicron variant of the coronavirus as it battles small-scale outbreaks in several regions, less than a month before the Games are due to kick off on Feb. 4.

The "closed-loop" bubble, in which participants can only leave if they are exiting the country or undergo quarantine, was activated earlier in January.

Restrictions at Games venues in Beijing and Zhangjiakou in neighbouring Hebei province will be much tighter than those during last summer's Tokyo Olympics.

But organisers have room to make adjustments to COVID-19 control measures if necessary, said Huang, at a briefing in Beijing.

As in Tokyo, no international spectators will be allowed at the Beijing Winter Games, and local attendance at event sites is likely to be curtailed, although specific arrangements have not been released.